(1)TRYPTOPHAN Lifetimes of APO D: It is known from the protein sequence that there are 4 tryptophans in this protein, and theoretical modeling studies indicate their critical importance in relation to the ligand binding pocket. Since the mechanism of hydrophobic ligand transport is a dominant function of this and presence and absence of ligand (BIS, cholesterol, steroids) binding. It would be of great advantage if the time resolved emission spectra could be obtained, since the tryptophan lifetime analysis is quite complicated. (2)Lifetime of BIS bound to APO D: We have established this as an important indicator ligand to probe the dynamics if ligand binding by stopped-flow and temperature jump. A 1:2 binding stoichiometry has been found. Lifetime information will be useful to understand possible multiple binding sites, the binding equilibria, and evaluation of FRET. Anisotropy measurements will also be undertaken.